/*
 * Copyright (C) 2008 Esmertec AG.
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.android.mms.util;

import android.util.Config;
import android.util.Log;

import java.util.HashMap;

public abstract class AbstractCache<K, V> {
	private static final String TAG = "AbstractCache";
	private static final boolean DEBUG = false;
	private static final boolean LOCAL_LOGV = DEBUG ? Config.LOGD : Config.LOGV;

	private static final int MAX_CACHED_ITEMS = 500;

	private final HashMap<K, CacheEntry<V>> mCacheMap;

	protected AbstractCache() {
		mCacheMap = new HashMap<K, CacheEntry<V>>();
	}

	public boolean put(K key, V value) {
		if (LOCAL_LOGV) {
			Log.v(TAG, "Trying to put " + key + " into cache.");
		}

		if (mCacheMap.size() >= MAX_CACHED_ITEMS) {
			// TODO Should remove the oldest or least hit cached entry
			// and then cache the new one.
			if (LOCAL_LOGV) {
				Log.v(TAG, "Failed! size limitation reached.");
			}
			return false;
		}

		if (key != null) {
			CacheEntry<V> cacheEntry = new CacheEntry<V>();
			cacheEntry.value = value;
			mCacheMap.put(key, cacheEntry);

			if (LOCAL_LOGV) {
				Log.v(TAG, key + " cached, " + mCacheMap.size() + " items total.");
			}
			return true;
		}
		return false;
	}

	public V get(K key) {
		if (LOCAL_LOGV) {
			Log.v(TAG, "Trying to get " + key + " from cache.");
		}

		if (key != null) {
			CacheEntry<V> cacheEntry = mCacheMap.get(key);
			if (cacheEntry != null) {
				cacheEntry.hit++;
				if (LOCAL_LOGV) {
					Log.v(TAG, key + " hit " + cacheEntry.hit + " times.");
				}
				return cacheEntry.value;
			}
		}
		return null;
	}

	public V purge(K key) {
		if (LOCAL_LOGV) {
			Log.v(TAG, "Trying to purge " + key);
		}

		CacheEntry<V> v = mCacheMap.remove(key);

		if (LOCAL_LOGV) {
			Log.v(TAG, mCacheMap.size() + " items cached.");
		}

		return v != null ? v.value : null;
	}

	public void purgeAll() {
		if (LOCAL_LOGV) {
			Log.v(TAG, "Purging cache, " + mCacheMap.size() + " items dropped.");
		}
		mCacheMap.clear();
	}

	public int size() {
		return mCacheMap.size();
	}

	private static class CacheEntry<V> {
		int hit;
		V value;
	}
}
